In accordance with the general practice within the oil and gas exploration industry, wells are drilled into the earth in hopes of recovering oil and gas from reservoirs. The drilling process involves the process of installing pipe from the reservoir to the surface. To achieve this, a reinforcing wall is established in the earth in the form of a protective pipe liner called a tubular within the well bore. The casing, in descending diameters, extends in many cases to hundreds of feet and may be cemented in place to ensure a pressure-tight connection between the surface and the oil and gas reservoir. Often cement is placed within the annulus located between the descending diameters, thereby insuring continuity and pressure integrity.
Usually the tubular remains within the well bore until it has been determined that no oil or gas reservoirs have been found or the reservoir has been exhausted. In cases where the well is to be plugged and abandoned, current law requires that the tubular must be removed and disposed of in a safe manner. In other cases the well may simply need to be drilled in a different direction and, if for some reason the drill bit cannot pass through the previously installed tubular due to an obstruction, the tubular must be removed before drilling operations can be restarted.
Removing drill tubular is very difficult because of the tremendous weight of the tubular strings and, in some cases, cement is located around and between the casings. In most wells there are at least four tubular strings, beginning with the largest, upper and outer most conductor pipe, the surface casing, the intermediate tubular and finally the production casing.
The plugging and abandonment of a well generally begins, in many cases, by first inspecting the well and insuring that the well is inactive and free of any residual gas and that the well is safe for removing the blow out preventors, well head, etc., above the tubing hangers. A safe work platform is established around the well head and various equipment is then used to create a bridge plug within the production tubular at a prescribed depth and applying cement thus sealing or plugging the well casing. The tubular is then cut at a prescribed depth below the surface using chemical cut, jet cut, etc., and a lifting device is then attached to the inner most tubular by screwing into or spearing the tubular tubing hanger. The production tubular is then lifted to a desired length, usually approximately forty feet, where either slips are set to hold the string and tongs are used to uncouple the tubular joints, or, two diametrically opposing holes are cut in the casing. In the latter case a bar is then inserted through the holes and the lifting device, such as a crane, is slaked off until the bar rests on top of the well flange. The tubular is then cut just above the bar and the initial section of tubular is then removed. The crane then returns and is attached to the bar thus lifting the tubular string for another length and holes are again cut for a lifting bar. The process is repeated until the tubular is removed. The process is then repeated for each tubular string until all of the casings have been removed. In some cases, where cement is present between the tubular strings, it becomes necessary to chip away the cement in order to cut the lifting bar holes.
Each incremental section of tubular usually requires operators to cut the casing, usually by torch, and manually drill two holes. The two holes are drilled from each side of the tubular in an attempt to keep them aligned with each other. It is essential that the holes be aligned with each other or large enough so that the bar or rod can be placed through the two holes. As discussed above, raising the tubular requires an extensive amount of force to overcome the resisting forces. Therefore, a stable platform is required. After the various increments of tubular are cut and pulled from the well bore, they are disposed of in a prescribed manner.
Holes drilled for the bar are individually and sequentially drilled in each incremental section of casing. The operators usually drill one side at a time, a slow and tedious process, especially with heavy gauge pipe. In some cases up to two hours is required. The operator is required to drill a second hole that is diametrically opposite the first. In some cases the operator is fortunate enough to get the two holes lined up, but at other times the two holes did not line up and a bar could not be inserted through both holes in which case a torch is used to enlarge at least one of the holes so that the bar could be placed through both holes.
A dual drill system that drills holes from both sides simultaneously thereby insuring alignment may be used. Although the time required to drill the holes may be drastically reduced, a significant amount of time is still required to set up, and clear, lubricate and repair the drill bits. In addition, a torch is still often used to cut each section of the tubular being removed. Since a torch is used to separate the tubular into reasonable lengths, it has become more prevalent to simply cut the holes with a torch as well.
In view of the above process a faster, more efficient method is needed to perform this task with greater certainty.
While certain novel features of an embodiment of this invention are described below and pointed out in the drawings and annexed claims, the invention is not intended to be limited to the details specified herein, since a person of ordinary skill in the relevant art will understand that various omissions, modifications, substitutions and changes in the forms and details of the device illustrated and in its operation may be made without departing in any way from the scope of the present invention. No feature of the invention is critical or essential unless it is expressly stated as being “critical” or “essential.”